Hi. I am writing a book and I was wondering if it is possible that a pandemic could form from lethal parasites getting into a country's watersupply?

If a parasite which is already known to be inside the major population mutates somewhere, does that mean that the majority of the population starts feeling symptoms of the mutated one instantly if infected with the mutated version or does it not matter whether it was there before or not.

This depends on what kind of parasites you have in mind. Is it bacteria, unicellular eukaryota or something multicellular?

I'm not sure what you mean by the first question. Of course each person is affected by the parasite they've got. Thus if they were infected with strain A, they will have symptoms of strain A; if they were infected with strain B, they will have symptoms of infection by strain B etc.

toxoplasmosa gondii. I am not sure which type of parasite this one is, but for my novel, I would like for it to mutate and be able to control humans as it does with rats. As roughly half of the population has this parasite dormant in their system, I suppose it wouldn't matter if one would mutate...Everyone would need to get infected again with the mutated strain, right?

By the way, the parasite does not simply mutate, it is weaponized and thus mutated by man.

And that is why I was wondering if the parasite could go into a country's watersupply and contaminate their water thus infecting a majority of the population as they drink and bathe in that contaminated water.

Maybe you have better ideas to as how the parasite could infect a large scale of people at once? In case my watersupply idea doesn't add up

Toxoplasmosa is actually "controling" humans. Check out work of prof. Jaroslav Flegr from Charles University, Prague, Czech Republic http://web.natur.cuni.cz/flegr/ (he may collaborate with the Oxford team mentioned in your link. I'm not sure now, whether they collaborate or compete.)

Anyway, yes, if it was mutated, all the humans had to be infected again to get the new strain. However, that could be done easily, if it's supposed to be a weapon. You only have to have some agents which will spread it around the biggest water reservoirs (maybe contaminate bottled water?)

How about a parasite that can travel with dense rain clouds. I know it seems impossible for a large parasite to cling onto a tiny molecule, but maybe they can use some sort of intermolecular force to "bond" to water.

Now, in my book, the CDC informs the ECDC of a potential parasite outbreak in Europe. Would the ECDC dispatch a team of epidemiologists to assess the threat or would they send a mixed team of (???) to assess the situation?

What kind of gear would they bring to analyze the parasite? I'll publish the first chapter and provide you with a password once I have these questions answered so that it can be as realistic as possible. It should be an interesting read for you guys, in case you like this sort of fiction